Recently, use of clouds has been advanced in companies, organizations and the like to speed up system construction, improve a use rate of computer resources, and the like. Furthermore, accompanying improvement of functions of cloud management software for providing a cloud environment, and the like, the number of companies which construct clouds in their own DCs (Data Centers) is increasing.
By deploying NAT (Network Address Translation) or the like at a boundary between an external network outside a cloud environment, for example, the Internet and an internal network of the cloud environment, the cloud management software provides the internal network with an IP address space different from that of the external network.
In general, a cloud administrator or the like configures an IP address pool (hereinafter referred to as an IP pool) obtained by pooling IP addresses of the external network. The cloud management software acquires an IP address from the IP pool in response to a request of a cloud user and adds a rule for converting the IP address and an IP address of the internal network to the NAT. Thereby, the cloud user can access a VM on the internal network from the external network.
It is ideally desirable that an IP address range of the IP pool is long and continuous. Actually, however, when an internal network is coupled to an existing external network such as a global network or an in-company network, a lot of short and continuous IP address ranges (hereinafter referred to as fragmented IP address ranges) are put into the IP pool. Therefore, it is necessary to flexibly add an IP pool.
In PTL 1, it is disclosed to deploy an edge gateway which provides network function such as a NAT function for each tenant, on a computer system.
In NPL 1, it is disclosed to deploy an edge gateway (NSX Edge and Edge Services Gateway) which provides network functions such as the NAT function, on a computer system similarly to PTL1.